fix(ember-table): run flexRender cell/header functions once per render pass#6452
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KevinVandy merged 1 commit intoJul 24, 2026
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…r pass The FlexRender components computed `result` in a plain getter that the template reads twice (component-branch check, then content), re-invoking the user's cell/header/footer render function on every read. Cache the getter so the render function runs exactly once per render pass.
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📝 WalkthroughWalkthroughFlexRender cell, header, and footer result getters now use Glimmer caching. A new integration test verifies that user-provided cell and header render functions are invoked only once per rendered result. ChangesFlexRender caching
Estimated code review effort: 2 (Simple) | ~10 minutes 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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pinging @rtablada for ember-review |
johanrd
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rtablada
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Jul 24, 2026
KevinVandy
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Jul 24, 2026
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🎯 Changes
The
resultgetter onFlexRenderCell/FlexRenderHeader/FlexRenderFooteris read by the template more than once (branch check + content), and a plain getter re-runs per read — so the user's render function executes 2× per render pass (3× for component cells).@cachedmakes it once, and guarantees the branch check and content see the same result.Prior art
svelte's FlexRender has the same branched template shape and memoizes with
$derived. All other adapters invoke the cell fn once per render pass (react/preact/solid render it as a component; vue calls it once).Measured (10k rows × 20 cols, virtualized, prod build): initial render 2,640 → 1,320 cell fn executions (= rendered cells).
Tests:
flex-render-invocation-count.test.gts— fails onbeta, passes here. Suite 27/27.✅ Checklist
pnpm test:pr.Cowritten by claude
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